Macroporous polypyrrole-TiO2 composites with improved photoactivity and electrochemical sensitivity.

Macroporous polypyrrole (PPy)-TiO2 composites were prepared by in situ oxidative polymerization of pyrrole in the macropores of TiO2. The formation mechanism of the PPy nanoparticles, including nucleation and further growth, was proposed by studying the particle growth process with increasing reaction time. The special growth process favors the formation of good cohesion and stabilized interface between the inorganic and organic phases. The conversion ratio of pyrrole monomer is in the range of 65.3-97.5%, and PPy content in the composites can reach as high as 21.04% with well preservation of the macroporous framework. Furthermore, dispersed PPy particles of ~100 nm in size can be obtained by etching the composites in HF acid, which is smaller than the PPy particles synthesized in the absence of the TiO2 template due to the pore-confinement effect. The composites show improved photoactivity on degradation of dye under simulated sunlight irradiation and electrocatalytic activity toward the detection of H2O2 in 0.1M phosphate buffer solution. Synergetic interaction between the two components and the porous structure is considered to be responsible for the enhanced properties of the new composites.